This grant proposes to study the physiological and behavioral correlates of neurons found in the recently described striosomal and matrix compartments of the neostriatal portion of the basal ganglia. The neostriatum is an important subcortical structure involved in the generation of motor behavior. Damage to the neostriatum and its associated basal ganglia structures results in several classical syndromes of motor and cognitive impairment, such as huntington's and Parkinson's disease. As yet, though, the precise functional role of the neostriatum is unknown. Recent anatomical studies have demonstrated that the neostriatum, which appears relatively homogeneous in the light microscope when stained with a Nissl stain, harbors a wealth of neurohistological complexity rivalling that found in any other brain structure. The neostriatum contains at least two distinct histologically defined compartments, the striosome and the matrix, which have distinct input and output connections. This dissimilar connectivity suggests these two compartments process different information and play different functional roles. The proposed experiments will; 10 describe the physiological characteristics of neurons in these two compartments and 2) will characterize the behavioral correlates of these neurons in the freely- moving, behaving rat, specifically examining sensory, motor and cognitive correlates of neuronal activity. Thus the experiments in this grant will provide a necessary foundation for beginning to understand the different roles of these newly defined structures and may give us new insights into the involvement of the neostriatum in motor behavior.